<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <!-- 开发环境版本，包含了有帮助的命令行警告 -->
  <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
</head>

<body>
  <div class="root">

    <div class="header">春晓 <button @click="show">{{msg}}</button></div>
    <div class="container" v-show="flag"> 春眠不觉晓，处处闻啼鸟。<br>
      夜来风雨声，花落知多少。</div>

  </div>
  <script>
    //创建vue实例
    new Vue({
      el: '.root', //指定当前vue 为哪个容器使用
      data: {
        msg: "展开",
        flag: false
      },
      methods: {
        show() {
          if (this.flag === true) {
            this.msg = '展开'
            this.flag = false
          } else {
            this.msg = '收起'
            this.flag = true
          }
        }
      }
    });

  </script>
</body>

</html>